1. Field of the Invention
The present invention relates to a transmission that changes the speed of the power of an engine. More particularly, the present invention relates to a transmission that shifts gears by a first shift clutch and a second shift clutch to which the power of the engine is transmitted.
2. Description of Background Art
A transmission including first and second shift clutches to which power of an engine is transmitted is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 6-17912. The transmission includes first and second clutches to which the power from an output shaft of the engine is transmitted, and a plurality of shifting systems for shifting gear steps. One of the shifting systems includes a change drum that is driven for rotation by a step motor, and the gear step is established at the time of engagement of the second clutch. In addition, each of the other shifting systems includes another change drum that is driven for rotation by another step motor, and the gear step is established at the time of engagement of the first clutch.
Incidentally, the provisions of the change drum and the step motor for each of the first and second clutches result in a large-scale transmission and an increase in cost.